小球藻多醣可能經由免疫調節作用具有改善帕金森氏症之效果

Abstract

帕金森氏症（Parkinson’s disease, PD）為常見之神經退化性疾病，研究發現帕金森氏症可能與中樞神經發炎相關，進而導致中腦黑質緻密區中多巴胺神經元大量死亡，引發黑質紋狀體路徑之多巴胺分泌不足所致。目前治療PD之主要藥物為左旋多巴胺，其機轉可使多巴胺合成增加，但卻無法減緩多巴胺神經元之持續性退化。因此，探尋具有調節發炎作用以致減緩多巴胺神經元持續性死亡之物質，可能為未來帕金森氏症之治療或預防提供新的策略。小球藻（Chlorella pyrenoidosa）為淡水單細胞藻類，由於富含蛋白質、維生素、次亞麻油酸及膳食纖維等營養成分，常作為膳食補充劑。小球藻多醣（Chlorella polysaccharides, CPS）已證實具有抗發炎及提升免疫力功效，然而，許多神經生理學研究亦指出周邊組織免疫反應和腦內發炎具有交互作用，故本研究以神經毒素1-甲基-4-苯基-1, 2, 3, 6-四氫吡啶（1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, MPTP）誘導之PD小鼠模式，探討小球藻多醣可否改善帕金森氏症與延緩病程發展，並以小鼠巨噬細胞RAW 264.7之體外試驗模式，尋找小球藻多醣之可能活性成分。結果顯示，小球藻多醣可減緩帕金森氏症小鼠之運動協調障礙、提升大腦紋狀體多巴胺及其代謝物含量、降低多巴胺轉換率、抑制多巴胺神經元減少以及抑制微膠細胞活化（microglial activation），並調節血清促發炎激素TNF-α、IL-1β與IL-6、血清二胺氧化酶及小腸內容物之分泌型免疫球蛋白A等周邊免疫指標。在體外試驗模式中，發現小球藻不可消化水溶性多醣（Chlorella indigestive polysaccharides, CIP）及其層析區分物，可降低以脂多醣（lipopolysaccharide, LPS）刺激巨噬細胞所生成之一氧化氮及前列腺素E2，並以酸性大分子多醣（large molecular weight acidic polysaccharides, LMA）具最佳之抗發炎活性，可抑制RAW264.7受LPS刺激所產生之促發炎激素素TNF-α、IL-1β與IL-6。綜合上述結果，小球藻多醣可由調節周邊免疫系統而降低腦內之神經發炎，增加紋狀體多巴胺之含量，以達到改善帕金森氏症並可能具有減緩病程發展之功效，並推測以LMA為最具代表之活性成分。

Neuroinflammation may play a role in the pathogenesis of Parkinson’s disease (PD), which is a common neurodegenerative movement disorder caused by the loss of nigral dopaminergic neurons. Major current treatment of PD is L-dopa, which can be the substitute of dopamine but unable to supress the neurodegeneration in the brain. Therefore, searching for components which can prevent the loss of dopaminergic neurons via regulating neuroninflammation may be a new strategy for the treatment or prevention of PD in the future. Chlorella pyrenoidosa is a single-celled alga often used as dietary supplement, with high nutritional value such as protein, vitamin, linolenic acid and dietary fiber. Polysaccharides from C. pyrenoidosa possessed great immunological activities, including anti-inflammatory and immune enhancement effects. However, its neuroprotective effects was not fully understood. Based on the proof that peripheral and brain inflammation are revelant, the objective of our study was to investigate the effects of C. pyrenoidosa polysaccharides (CPS) in a mouse model of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD. In addition, our study screened for the polysaccharides fraction with the greatest immunomodulatory activities through LPS-induced inflammation model in RAW 264.7 cell. Our results indicated that CPS showed neuroprotective effects by reducing the behavioral deficits, increasing the contents of striatal dopamine (DA) as well as its metabolites DOPAC and HVA, and inhibiting DA turnover ratio, tyrosine hydroxylase loss as well as microglial activation. Moreover, CPS suppressed the production of serum cytokines TNF-α, IL-1β and IL-6 and enhance the peripheral immunomodulatory biomarkers such as serum diamine oxidase and small intestinal secretory immunoglobulin A in PD mice. In cell model, our research showed that Chlorella indigestive polysaccharides (CIP) and its chromatography fractions decreased LPS-induced nitric oxide (NO) and PGE2. Furthermore, the large MW acidic polysaccharides (LMA) from CIP had the greatest anti-inflammatory effects, including the inhibition of NO, PGE2 and cytokines TNF-α, IL-1β and IL-6 levels in LPS-induced RAW 264.7 cell. Taken together, these findings demonstrated that CPS could delay the disease progression in PD via its immunomodulatory action, and LMA might be its active component.